1. Field of the Invention
The present invention is directed to an input window for a radiographic image intensifier as well as to a method for making such an input window.
2. Description of the Prior Art
German PS 43 42 219 discloses a radiographic image intensifier with an input window wherein a layer of luminous material is deposited on a carrier, this layer converting the incident x-rays into light. A photocathode is usually vacuum evaporated (metallized) on the layer of luminous material, this photocathode converting the light that emanates from the layer of luminous material into electrons. The electrons are opto-electronically projected onto the output window, which is situated opposite the input window. The output window is formed as an output luminescent screen by means of which the energy of the electrons is converted into light, which is detected by a downstream camera, for example, and this light is displayed at a display apparatus via an image intensifier video chain as an image of a transirradiated subject. As a substrate, the aforementioned carrier consists of an aluminum sheet to which a collar form is imparted by rolling, deep-drawing or roll-pressing. In known fashion, the inner concave surface of the collar-shaped substrate must be optimally smooth and/or structurally homogenous, so that in the evaporation of a luminous layer consisting of cesium iodide, for example, the cesium iodide grows uniformly in the column structure.
It is an object of the present invention to provide an input window for a radiographic image intensifier and a method for making it wherein the substrate has a smooth and structurally homogenous surface on which the uniform growth of the crystal structure is possible.
This object is achieved in accordance with the principles of the present invention in an image intensifier having an input window and a method for making same wherein an intermediate layer is deposited on a substrate for a luminous layer, smoothing the surface of the substrate. The surface flaws and damaged locations, as well as unevenness and fissures, holes and depressions which are brought about in the rolling, deep-drawing or roll-pressing, are compensated by the intermediate layer, so that there is a good base for the growth of the crystal structure of the luminous substance on the intermediate layer.